Constant-velocity-ratio universal joints

ABSTRACT

A fixed, ball-type constant velocity joint includes an outer member (10) having ball-receiving tracks (17) and lands (18) between the tracks. The lands engage the external surface (21) of a cage (12) and are provided with relief portions (25) which extend across the whole circumferential widths of the lands. The relief portions are located between first and second contacting portions of the external cage surface and the facing land surfaces. The provision of the relief portions facilitates the formation of the land surfaces by reducing the area which has to be accurately shaped. The lands are hardened but before hardening may be provided with the relief portions (25). After hardening no treatment to remove metal is applied to the surfaces in which a relief portion has been provided except, optionally, for the removal of scale produced by

TECHNICAL FIELD

This invention relates to fixed (i.e. non-plunging)constant-velocity-ratio universal joints, of the kind which comprises:

an outer joint member of hollow configuration, having a rotational axisand in its interior a plurality of at least partially arcuate trackscircumferentially spaced about said axis and whose centre lines extendin meridian planes relative to said axis, there being lands definedbetween said tracks and integral with the outer joint member, the landshaving radially-inwardly directed surfaces;

an inner joint member disposed within the outer joint member and havinga rotational axis, the inner joint member being provided on its exteriorwith a plurality of tracks whose centre lines lie in meridian planeswith respect to the rotational axis of the inner joint member and whichface the tracks in the outer joint member in opposed pairs, there beinglands defined between the tracks on the inner joint member, thelast-mentioned lands having radially-outwardly directed surfaces;

a plurality of balls disposed one in each pair of facing tracks in theouter and inner joint members for torque transmission between themembers;

a cage of annular configuration disposed between the joint members andhaving openings in which respective balls are received and constrainedso that their centres lie in a common plane; the cage having externaland internal surfaces each of which cooperates with the land surfaceswhich face it to locate the cage and the inner joint member axially;

the configuration of the tracks in the outer and inner joint members,and/or the internal and external surfaces of the cage, being such thatwhen the joint is articulated the common plane containing the centres ofthe balls (the bisector plane) is caused substantially to bisect theangle between the rotational axes of the joint members.

Such a joint will hereinafter be referred to as "a joint of the kindspecified".

DESCRIPTION OF RELATED ART

There are several types of joint of the kind specified, differing fromone another, inter alia, in respect of the arrangement and configurationof the tracks in the joint members and/or of the internal and externalsurfaces of the cage whereby the common (bisector) plane is guided asaforesaid thereby giving the joint constant-velocity-ratio operatingcharacteristics. What such different types of joints have in common,however, is that the cage is located axially in the joint by cooperationbetween the external cage surface and the surfaces of the lands facingsuch cage surface.

Theoretically, in a joint of the kind specified, these cooperatingsurfaces should be part-spherical and there should be a very closeconformity between the shape of the external surface of the cage and thecomplementary surfaces on the lands on the outer joint member with whichit cooperates (sufficient clearance being provided only for a film oflubricant therebetween). In practice such close conformity is verydifficult to achieve within the normal allowable tolerances.

When torque is being transmitted by the joint, the forces acting in thejoint cause the cage to be urged towards one end of the joint; which endwill depend on the respective directions of the offsets of the tracks inthe inner and outer joint members from said common plane when the jointis in its unarticulated position. If the cooperating surfaces on thecage and the lands of the outer joint member, which in theory should bepart-spherical, are not ground accurately, the forces acting in thejoint can cause the cooperating surfaces on the cage and the lands totend to become jammed together with a wedging action. Thus for exampleif the inwardly facing surfaces of the lands on the outer joint memberare, in longitudinal cross-section through the joint, of a larger radiusof curvature than the cooperating outwardly facing surface of the cage,the joint may run with the cage continually in a condition of incipientjamming. The result is generation of heat and rapid wear.

This problem can be overcome by designing one or both surfaces of thecooperating pair to be not truly part-spherical about the rotationalaxis of the component whereon it is provided, but instead a surface ofrevolution about said axis of an arc whose centre of curvature is not onsuch axis but is offset therefrom. The aim is to achieve cooperatingsurfaces which contact one another in end regions only of the componentswhereon they are provided. To achieve this, in longitudinal section theradius of curvature of the inwardly facing cooperating surfaces of thelands should be slightly less than the radius of curvature of theoutwardly facing cooperating surface of the cage. It is important thatthe difference in such radii of curvature should not be too greatotherwise the contact areas between cage and the outer joint member willbe small giving rise to high pressures and rapid wear. This combinationof surface radii of curvature permits greater tolerances to be allowedin manufacture than if one tried to grind the surfaces to the same radiiof curvature but, even so, very tight control of the tolerances in theconfiguration of the surfaces is still necessary which rendersproduction difficult.

Accordingly, it is an object of the present invention to provide auniversal joint of the kind specified in which this problem is overcomeor ameliorated.

DESCRIPTION OF INVENTION

According to one aspect of the present invention we provide a joint ofthe kind specified wherein, when the joint is transmitting torque, thereare first contacting portions of the external surface of the cage andthe facing land surfaces of the outer joint member adjacent one end ofthe outer member which are in contact and resist the axial forces on thecage due to the joint geometry, wherein there is a relief portion (ashereinafter defined) located, when the joint is in its unarticulatedposition, generally adjacent to the common (bisector) plane andpreferably either between the first contacting surface portion in eachof said facing land surfaces and the common plane or about the commonplane, each relief portion extending across the whole circumferentialwidth of the land between the tracks that border the land, and whereinthere are second contacting portions of the external cage surface andthe facing land surfaces of the outer joint member to control the axialfloat of the cage and which are separated from the first contactingportions by the relief portions.

By "relief portion" of an outer joint member land surface we mean asurface portion of the outer joint member land which, duringarticulation and use of the joint to transmit torque, does not contactthe facing external surface of the cage and which:

is separated from the adjacent first contacting surface portion by astep in the surface of the component or an abrupt change in the gradientof said surface in longitudinal section; or

is defined by a surface or surfaces the or each of which has a differentradius of curvature from the surface of the adjacent first contactingsurface portion and which may be tangential to the surface of said firstcontacting surface portion; or

in longitudinal section is straight; or

is defined by a surface which in longitudinal section meets the surfaceof the adjacent first contacting surface in a point of inflexion.

By "longitudinal section" we mean a section in a plane through therotational axis of the joint when it is in its unarticulated position.

In present designs of joints of the kind specified it is contact betweeninappropriately-shaped surfaces of the cage and a joint member in anaxial mid-region of such components which is largely the source of thejamming problem.

According to another aspect of the present invention we provide a jointof the kind specified wherein, when the joint is transmitting torque,there are first and second hardened contacting portions of the externalcage surface and the facing land surfaces of the outer joint member, thefirst contacting portions being adjacent to one end of the joint andbeing in contact to resist the axial forces on the cage due to the jointgeometry and the second contacting portions controlling the axial floatof the cage and wherein there is a relief portion (as hereinbeforedefined) between the first and second contacting surface portions acrossthe whole of the circumferential width of each of said facing landsurfaces, the or each of said relief portions being located generallyadjacent to the common (bisector) plane when the joint is in itsunarticulated position and wherein said relief portions have beenproduced in said land surfaces before the latter have been hardened andwherein, after hardening, no treatment to remove metal has been appliedto said land surfaces in which a relief portion has been providedexcept, optionally, for the removal of scale produced by said hardening.

We also provide a method of making an outer joint member of a joint ofthe kind specified in a finished state ready for use in said jointcomprising making a blank for the member, simultaneously or sequentiallyproducing the tracks, the lands and a relief portion (as hereinbeforedefined) in the surface of each of said lands, said relief portionextending across the whole circumferential width of the land and beinglocated generally adjacent to the common (bisector) plane when the jointis in its unarticulated position and heat treating the member to hardenthe surfaces of the lands but applying no further treatment to said landsurfaces to remove metal therefrom after hardening of the member except,optionally, for the removal of scale produced by said hardening.

Various prior proposals have been made in which there is a reliefbetween various parts of the joint.

Thus Japanese Utility Model 3-112123 describes a plunging constantvelocity joint in which there is a relief on the inner member and/or theinner surface of the cage to act as a lubricant reservoir.

U.S. Pat. No. 5,433,668 describes a fixed, ball-type, constant velocityjoint in which the axial clearance of the cage in the outer joint memberis adjusted by fingers on a ring, the ends of the fingers engaging theexternal surface of the cage and the ring being secured to the lands ofthe outer joint member at the open end thereof, The cage only contactsthe fingers and does not contact the outer joint member.

U.S. Pat. No. 4,820,240 describes a fixed, ball-type constant velocityjoint in which there is an axial clearance between the facing surfacesof the inner joint member and the cage and wherein the facing surface ofthe cage and the outer member comprise a spherical guide surface and ashort bearing surface.

U.S. Pat. No. 4,156,353 discloses a fixed, ball-type constant velocityjoint in which the external surface of the cage and the facing landsurfaces of the outer joint member are only in contact adjacent to theopen end of the joint and the external surface of the inner joint memberand the internal surface of the cage are only in contact adjacent to theclosed end of the joint.

None of these proposals solves the problem set out above whilecontrolling the axial float of the cage.

By virtue of the relief portions in joints embodying the invention, thearea of potential cage/outer joint member contact is reduced to wherecontacting surface portions are required. thus the very tight tolerancesneeded to provide different radii of curvature on the facing surfaces toprevent wedging and jamming of the cage relative to the outer jointmember is avoided. This facilitates manufacture and the ability to copewith differences in the amount of stock to be removed from differentparts of a component when providing the sphere form of the land surfacesin the outer joint member.

Thus in the longitudinal cross-section of a joint embodying theinvention the configuration of the contacting surface portions of theouter joint member and the cage becomes less critical. The contactingsurface portions can be designed to be truly part-spherical, withadvantages in achieving contact therebetween over relatively largesurface areas (thus reducing wear) whilst avoiding the wedging problem.

Preferably, each of the first contacting surface portions issubstantially part-spherical. To aid manufacture, each of the secondcontacting surface portions is preferably also substantiallypart-spherical. The first and second contacting surface portionspreferably lie on the same part-spherical surface centred on therotational axis of the outer joint member.

Preferably only the land surfaces of the outer joint member have reliefportions.

As stated above the relief portions may extend on both sides of saidcommon plane when the joint is in its unarticulated position or mayextend only on one side of said plane between the common plane and theadjacent first contacting surfaces.

Preferably in the manufacture of joints or outer joint members embodyingthe invention the contacting portions and relief portions are producedwith the components in their soft state i.e. before hardening. Becausethe area of potential cage-joint member contact is reduced, changes fromthe spherical form of the member arising from the heat treatment ofhardening can be accommodated more readily. If the spherical surfacesare machine generated rather than machine formed (e.g. by turning ratherthan form grinding) faster cycle times can be realised as the slow feedrates are required over shorter distances. On the other hand where theland surfaces are machine formed lower tooling costs may result as thereis less area to form.

The combination of the provision of the relief portions in the outermember and their formation prior to heat treatment and the fact that nosurface treatment to remove metal is applied to the surfaces having therelief portions after heat treatment, except possibly de-scaling,eliminates costly post-heat treatment machining operations of the landssuch as grinding.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is an end view of a fixed constant-velocity-ratio joint embodyingthe invention taken in the direction of the arrow A in FIG. 2;

FIG. 2 is a longitudinal section through the joint of FIG. 1 on the lineII--II of FIG. 1;

FIG. 3 is an enlarged portion of the section of FIG. 2 showing a reliefportion in more

FIGS. 4, 5 and 6 are detail drawings similar to FIG. 3 showing othershapes of relief portion; and

FIGS. 7 to 11 illustrate one method of making an outer member for afixed joint of the kind specified.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring firstly to FIGS. 1 and 2 of the drawings, these show a fixedconstant-velocity-ratio joint whose principal components are an outerjoint member indicated generally at 10, an inner joint member 11, a cage12 and a plurality of torque-transmitting balls 13.

The outer joint member 10 is a hollow cup-shaped component with a closedend 14 from which a stub shaft 15 extends. The axis of rotation of theouter joint member is indicated at 16. In the interior of the outerjoint member there is a number of circumferentially spaced arcuatetracks 17 which are equi-angularly spaced about the joint member axisand whose centre lines lie in meridian planes containing the axis 16.Between the tracks 17 there are defined lands 18 which are integral withthe joint member and have radially inwardly directed surfaces.

The inner joint member 11 is provided on its exterior surface with anumber of arcuate tracks 19 whose centre lines lie in meridian planescontaining the axis of rotation of the inner joint member which, whenthe joint is in the aligned (non-articulated) condition illustrated, iscoincident with the axis 16. The tracks 19 face the tracks 17 in opposedpairs. Between the tracks 19 the inner joint member has lands 23 whichare integral with the inner joint member and have radially outwardlydirected surfaces. The inner joint member 11 is a hollow component,having a splined bore 24 for torque-transmitting reception of a driveshaft 24a.

In the longitudinal cross-section shown in FIG. 2, the tracks 17, 19 arearcuate in configuration and the centres of curvature of such arcs areoff-set from one another axially of the joint so that the tracks of eachpair diverge from one another as they approach the open end of the outerjoint member. Each pair of opposed tracks 17, 19 receives a respectivetorque-transmitting ball 13, the centres of the balls lie in a commonplane P. The offset configuration of the tracks 17, 19 in the jointmembers is such that, in known manner, when the joint is articulated thecommon plane P (the bisector plane) in FIG. 2 is caused to bisect theangle between the rotational axes of the joint members, thereby givingthe joint constant-velocity-ratio characteristics.

The cage 12 is an annular component interposed between the inner andouter joint members. It has a plurality of openings 20 respectivelyreceiving the balls 13 so that the centres of the balls lie in thecommon plane P.

The cage has an external surface 21 which contacts the radially-inwardlyfacing surfaces of the lands 18 between the tracks 17 of the outer jointmember. The cage also has an internal surface 22 engageable with theradially-outwardly facing surfaces of the lands 23 between the tracks 19in the inner joint member 11.

When the joint is in use, forces acting on the balls and thus on thecage urge the latter towards the open end of the outer joint member 10.Thus the external surface of the cage bears on the facing surfaces ofthe lands 18 of the outer joint member primarily in an area Dimmediately adjacent the open end of the outer joint member. In thejoint shown the offset of the tracks in the inner member 11 is towardsthe closed end 14 of the outer joint member 10 and the offset of thetracks in the outer joint member is towards the open end of the outermember. However the direction of the offsets could be reversed whichwould change the location of the first contacting surface portions to aposition adjacent to the closed end of the outer joint member.

The surfaces of the lands 18, 23 are preferably part-spherical, formingparts of a sphere centered on the axis of rotation 16 of the outermember 10 or the inner member 11 respectively. However the land surfacesmay be formed of surfaces of revolution of a circular arc about saidaxes but with the arc not being centered on the axis. In anotherarrangement the arc is not circular. The land surfaces couldalternatively be formed by surfaces of revolution of an arc, which ispreferably but not necessarily circular, about an axis of revolutionoffset from said axes of rotation of the members, the locus of the axisof revolution, when considering all the land surfaces, being a circlearound the axis of rotation. As will be clear to one skilled in the art,any departure of the land surfaces from true part-spherical surfacescentred on the axes of rotation will be small.

In the embodiment of the invention shown in FIGS. 1 and 2, the inwardlyfacing surfaces of the lands 18 of the outer joint member are relievedas indicated at i5. The relief portion extends on both sides of thecommon plane P when the joint is in its unarticulated position shown inFIG. 2 and its ends are defined by steps. Each relief portion extendsacross the whole width of the land between the tracks on either side ofthe land.

In FIG. 3, the step in the surface at which each such relief portionstarts adjacent to the open end of the outer joint member is indicatedat 26 and the opposite end is indicated by a step 26a. This leaves firstcontacting surface portions 27 of the land surfaces between the reliefportion 25 and the open end of the outer joint member. These portions 27contact the external surface 21 of the cage. The engagement of thesurface portions 27 with the external surface of the cage resists theaxial forces on the cage which occur during operation of the joint.

Each relief portion 25 may have a depth no greater than 150 microns(0.150 mm), e.g. between 50 and 100 microns, with respect to the landsurface at the ends of the relief. A preferred depth range is between 30and 100 microns. The relief portions should be as shallow as possiblewhilst preventing the outer cage surface from coming into contact withthe inwardly facing surface of the relief portion during use andarticulation of the joint and should not be so deep as to reduce thedepth of the tracks in the outer joint member to the extent thatdisadvantageous contact conditions between the balls and the tracksresult. The provision of the relief portions reduces the surfaceportions on the lands which have to be shaped accurately to the portions27 thus easing production.

The provision of the relief portions has the effect that any tendencyfor the cage to operate in a state of incipient wedging or jammingrelative to the outer joint member is substantially avoided without thenecessity to hold tight tolerances over the whole of the lands on theouter joint member. The cage is still satisfactorily guided by virtue ofits contact, under torque transmission, with the unrelieved firstcontacting portions 27 of the lands 18 immediately adjacent the open end10 of the outer joint member.

A further effect of the provision of the relief portions 25 inaccordance with the invention is that they afford reservoirs forlubricant adjacent to cooperating surfaces of the cage and outer jointmember so that lubrication of such surfaces may be improved.

Yet a further effect of the provision of the relief portions is thatwhen the joint is subject to high torque, under which conditions itmight be possible for the high radial forces to distort tile outer jointmember to an out-of-round condition the cage is less liable to besquashed by the outer joint member. If the relief portions were notpresent, the distortion of the outer joint member could cause it totighten on the cage.

Referring again to FIGS. 1 and 2 the cooperation of the contactingsurface portions 27 on the lands of the outer joint member with theexternal surface 21 of the cage resist the axial forces on the cageduring operation of the joint. To control axial float of the cagerelative to the outer joint member there are second surface portions 127on the lands 18 adjacent the closed end of the joint which engage theexternal surface 21 of the cage. The surfaces 27 and 127 on each land ofthe outer joint member are separated by the relief portion 25. It is tobe noted that the relief portion 25 extends on both sides of the commonplane P when the joint is in its unarticulated position. However therelief portion could merely extend between the contacting portions 27and the common plane P.

In the production of joints embodying the invention, there is no need tocontrol the configuration of the lands in the outer joint member overthe same area as would be necessary if the lands were of unrelievedgenerally part-spherical configuration. The cooperating internal andexternal surfaces of the outer joint member lands and cage respectivelymay be designed to be exactly part-spherical, i.e. surfaces ofrevolution about the rotational axes of the respective components ofcircular arcs whose centre of curvature lies on such rotational axis.Thus better cooperation ii the portions of such surfaces which do makecontact with one another can be achieved.

The relief portions shown in FIGS. 1-3 are defined between steps in thesurface in which they are provided, these steps are constituted by anabrupt change in gradient in the surface; the change in gradient couldbe of any convenient angle

FIG. 4 shows diagrammatically another arrangement. Surface portions 30and 31 are the first and second contacting surfaces on the innersurfaces of the lands of the outer joint member and are circular arcs ofthe same radius struck from point A on the rotational axis 16 of theouter joint member. The relief portion is defined by surfaces 32 and 33which are circular arcs struck from points B and C respectively offsetfrom the axis 16. The arcs 32 and 33 defining the relief portion areblended where they meet and are tangent to the surface portions 30 and31 respectively. It will be seen that the relief portions are locatedabout the common plane P when the joint is in its unarticulated position

In FIG. 5 surface portions 34 and 35 are the first and second contactingsurface portions on the external surface of the cage and the lands ofthe outer joint member. The relief portion 36 is defined by end portions37 and 38 of a different shape to the portions 34 and 35 which areconnected by an arcuate surface portion 39 centred on the rotationalaxis of the joint but of greater radius than the radius of the externalsurface of the cage. Portions 34 and 37 meet at a point of inflexion asdo portions 35 and 38. Again the relief portion is located about thecommon plane P when the joint is in its unarticulated position.

In FIG. 6 surface portions 40 and 41 are the first and second contactingportions on the external surface of the cage and the lands of the outermember. The relief portion 42 is defined by two surface portions 43 and44 which are straight in cross-section and which are blended at 45. Atthe ends 46 and 47 of the surface portions 43 and 44 these are tangentto the land surface 41. The relief portion is located about the commonplane P when the joint is in its unarticulated position.

The relief portions need not be symmetrical as shown. They could becomposed of different shapes at their ends for example a step as shownin FIG. 3 at one end and a straight line shape as in FIG. 6 at the otherend. Other combinations are possible but in all cases the reliefportions extend across the whole width of the lands between the trackson either side. They may be located about the common plane P or betweenthe plane P and the first contacting surface portions, in each case whenthe joint is in its unarticulated position.

In each embodiment, the parts of the surface of each land 18 on eitherside of the relief portions 25; 32,33; 36 and 42 are preferably parts ofthe same spherical surface or surface of revolution as discussed above.However the parts could lie on different surfaces of revolution ifdesired.

The illustrated fixed joint is one in which the external and internalpart-spherical surfaces of the cage are concentric with one another. Insome fixed joints, such surfaces are not concentric and the cage isthicker at one end than at the other. The present invention is equallyapplicable to such joints.

Referring now to FIGS. 7 to 11, one method of manufacture of an outermember as shown in FIGS. 1 to 3 will be described.

Referring to FIG. 7, this shows a plain bore forging 50. This is aforging having a bell shaped portion 51 with a stem 52. The firstoperation is to centre drill at 53 the end 54 of the stem.

Referring now to FIG. 8, the next step is to turn the outside profile ofthe forging. Thus the outer surface of the bell 51 is machined toprovide a groove 55 to receive a boot clamp. The stem is machined at 57to provide a stub shaft which is subsequently splined and the endportion 58 of the stem is turned down and will be subsequently threaded.

Referring now to FIG. 9, the third step is to produce a sphericalsurface or sphere form 59 inside the bell and to machine the front face65 and mouth chamfer 66 of the outer member. The spherical surface 59will ultimately provide the land surfaces between the tracks after thesehave been milled in the next step. The sphere form 59 is relieved at 60adjacent the closed end of the outer joint member. Also the sphere formis provided with a circumferential relief groove 61 about the commonplane P as described above. The cross section of the relief groove canbe of any of the shapes described in relation to FIGS. 1 to 6 but theshape shown is that shown in FIGS. 2 and 3.

Referring to FIG. 10, the tracks 62 are now milled in two stages. Firsta rough milling and then a finish milling. The production of the tracksdefines the lands between them and each of the lands has a reliefportion 61a provided by the groove 61. FIG. 11 shows the tracks 62 andthe intervening lands 63. As will be clear from FIGS. 9 and 10 therelief portions extend across the whole circumferential width of thelands between adjacent tracks.

After the tracks have been milled the spline is rolled on the part ofthe stem 57 and the thread rolled on the part of the stem 58.

The outer member is now subjected to a heat treatment operation toharden the track and land surfaces. The heat treatment operation may,for example, be induction hardening or case carburising. After hardeningno surface treatment to remove metal is applied to the surfaces of thelands 63 except, optionally, the removal of scale produced by thehardening operation. If desired the tracks can be machined or ground.

Thus it will be seen that the lands with their relief portions are notsubject to any expensive post-heat treatment operation and this is madepossible by the provision of the relief in the lands which cuts down thecontacting areas of the lands and the outer surface of the cage.

The outer member could be produced in other ways, for example it couldbe forged with rough lands and tracks and then the lands would be turnedto the required shape and the tracks milled. During the turning of thelands the relief portions would be also created. After splining andthreading, the outer member would be heat treated but no metal removingoperation would be applied to the land surfaces after heat treatmentexcept, optionally, to remove the scale from the land surfaces.

In yet another method of manufacture of the outer member, it would bepossible to precision form the outer member and finish form the lands tothe required shape, including the reliefs, while roughly producing thetracks. The tracks would then be finish milled and the outer member heattreated to harden the tracks and lands but no further surface treatmentwould be applied to the land surfaces except, optionally, to remove theheat treatment scale. In an alternative method the tracks could befinish formed by precision forming and the lands then turned with thereliefs, the component heat treated and the land surfaces subject, ifdesired, to scale removal operations but no metal removal.

It would also be possible to finish form the lands and trackssimultaneously. The relief portions could be produced with the lands orsubsequently machined. After heat treatment there would be no furthermetal removal steps applied to the lands except optionally for scaleremoval.

After heat treatment the outer member could be calibrated, e.g. bycoining and could be coated in whole or in part with e.g. titaniumnitride or zinc phosphate.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

What is claimed is:
 1. A fixed (i.e. non-plunging)constant-velocity-ratio universal joint, comprising:an outer jointmember (10) of hollow configuration having a rotational axis (16), aplurality of at least partially arcuate tracks (17) circumferentiallyspaced about said axis (16) in the interior of the outer joint memberand having centre lines extending in meridian planes relative to saidaxis, lands (18) defined between said tracks and which are integral withthe outer joint member and have radially-inwardly directed surfaces; aninner joint member (11) disposed within the outer joint member andhaving a rotational axis, a plurality of at least partly arcuate tracks(19) on the exterior of the inner joint member, having centre linesextending in meridian planes with respect to the rotational axis of theinner joint member and which face the tracks (17) in the outer jointmember in opposed pairs, lands (23) defined between the tracks on theinner joint member, the lands on the inner joint member havingradially-outwardly directed, surfaces; a plurality of balls (13)disposed one in each pair of facing tracks (17, 19) in the outer andinner joint members for torque transmission between the members; a cage(12) of annular configuration disposed between the inner and outer jointmembers (11, 10) and having openings (20) in which respective balls (13)are received and constrained so that their centres lie in a common plane(P); the cage having external and internal surfaces (22, 21) whichengage the land surfaces on the outer and inner joint membersrespectively; first contacting portions (27, 30, 343, 40) of theexternal surface (21) of the cage and the facing surfaces of the lands(18) of the outer joint member adjacent one end (A) of the outer jointmember which are in contact when the joint is transmitting torque andresist the axial forces on the cage due to the joint geometry, at leastone of the configurations of the tracks (17, 19) in the outer and innerjoint members, and the internal and external surfaces (21, 22) of thecage, being such that when the joint is articulated said common plane(P) is caused substantially to bisect the angle between the rotationalaxes of the joint members; characterised in that there is a reliefportion (25; 32, 33; 36; 42) in each of said land surfaces of the outerjoint member located, when the joint is in its unarticulated position,adjacent to the common plane (P), each relief portion comprising asurface portion (32, 33; 37, 38, 39; 43-47) of the outer joint memberwhich, during articulation and use of the joint to transmit torque, doesnot contact the facing external surface of the cage and which extendsacross the whole circumferential width of the land (18) between thetracks (17) that border the land; and in that there are secondcontacting portions (127, 31, 35, 41) of the facing surfaces of thelands (18) of the outer joint member and of the external cage surface(21) to control the axial float of the cage and which are separated fromthe first contacting portions by the relief portions (25; 32, 33; 36;42).
 2. A fixed (i.e. non-plunging) constant-velocity-ratio universaljoint, comprising:an outer joint member (10) of hollow configurationhaving a rotational axis (16), a plurality of at least partially arcuatetracks (17) circumferentially spaced about said axis (16) in theinterior of the outer joint member and having centre lines extending inmeridian planes relative to said axis, lands (18) defined between saidtracks and which are integral with the outer joint member and haveradially-inwardly directed surfaces; an inner joint member (11) disposedwithin the outer joint member and having a rotational axis, a pluralityof at least partly arcuate tracks (19) on the exterior of the innerjoint member, having centre lines extending in meridian planes withrespect to the rotational axis of the inner joint member and which facethe tracks (17) in the outer joint member in opposed pairs, lands (23)defined between the tracks on the inner joint member, the lands on theinner joint member having radially-outwardly directed, surfaces; aplurality of balls (13) disposed one in each pair of facing tracks (17,19) in the outer and inner joint members for torque transmission betweenthe members; a cage (12) of annular configuration disposed between theinner and outer joint members (11, 10) and having openings (20) in whichrespective balls (13) are received and constrained so that their centreslie in a common plane (P); the cage having external and internalsurfaces (22, 21) which engage the land surfaces on the outer and innerjoint members respectively; first contacting portions (27, 30, 343, 40)of the external surface (21) of the cage and the facing surfaces of thelands (18) of the outer joint member adjacent one end (A) of the outerjoint member which are in contact when the joint is transmitting torqueand resist the axial forces on the cage due to the joint geometry, atleast one of the configurations of the tracks (17, 19) in the outer andinner joint members, and the the internal and external surfaces (21, 22)of the cage, being such that when the joint is articulated said commonplane (P) is caused substantially to bisect the angle between therotational axes of the joint members; characterised in that there is arelief portion (25; 32, 33; 36; 42) in each of said land surfaces of theouter joint member located, when the joint is in its unarticulatedposition, either between the first contacting surface portion (27, 30,34, 40) of the land surface and said common plane (P) or about saidcommon plane, each relief portion comprising a surface portion (32, 33;37, 38, 39; 43-47) of the outer joint member which, during articulationand use of the joint to transmit torque, does not contact the facingexternal surface of the cage and which: is separated from the adjacentfirst contacting surface portion (27) by an abrupt change in thegradient of said surface in longitudinal section which may form a step(26); or is defined by a surface or surfaces (32, 33) the or each ofwhich has a different radius of curvature from the surface of theadjacent first contacting surface portion (30) and which may betangential to the surface of said first contacting surface portion; orin longitudinal section (43, 44) is straight; or is defined by a surfacewhich in longitudinal section meets the surface of the adjacent firstcontacting surface in a point of inflexion (34, 37), each relief portionextending across the whole circumferential width of the land (18)between the tracks (17) that border the land; and in that there aresecond contacting portions (127, 31, 35, 41) of the facing surfaces ofthe lands (18) of the outer joint member and of the external cagesurface (21) to control the axial float of the cage and which areseparated from the first contacting portions by the relief portions (25,32, 33), 36; 42).
 3. A joint according to claim 1 wherein said first andsecond contacting portions (27; 32, 33; 34; 35; 40; 41; 127) of thesurfaces of the lands (18) on the outer joint member are hardened,characterised in that said relief portions (25, 32, 33, 36, 42) havebeen produced in the surfaces of said lands (18) before the latter havebeen hardened and wherein, after hardening, no treatment to remove metalhas been applied to the surfaces in which a relief portion has beenprovided except, optionally, for the removal of scale produced by saidhardening.
 4. A joint according to claim 1 wherein each of the firstcontacting surface portions (27, 32, 34, 40) on the outer joint memberis substantially part-spherical.
 5. A joint according to claim 1 whereineach of the second contacting surface portions (127, 33, 35, 41) on theouter joint member is substantially part-spherical.
 6. A joint accordingto claim 4 wherein the first and second contacting surface portions (27,32, 34, 40;127, 33, 35, 41) on the outer joint member lie on the samepart-spherical surface centred on the rotational axis (16) of the outerjoint member.
 7. A joint according to claim 1 wherein the firstcontacting portions and the second contacting portions of the landsurfaces respectively do not lie on the same part-spherical surface orsurface of revolution.
 8. A joint according to claim 1, wherein theexternal surface of the cage does not have relief portions.
 9. A jointaccording to claim 1 wherein the depth of each relief portion is nogreater than 150 microns with respect to the land surface at the ends ofthe relief portion.
 10. A joint according to claim 9 wherein the depthof each relief portion is between 50 and 100 microns with respect to theland surface at the ends of the relief portion.
 11. A joint according toclaim 9 wherein the depth of each relief portion is between 30 and 50microns with respect to the land surface at the ends of the reliefportion.
 12. An outer joint member of a fixed joint as claimed in claim1 in a finished state ready for use in said joint and having hardenedland surfaces, characterised in that said relief portions (25; 32, 33;36; 42) have been produced in the lands (18) of the member before thesurfaces of the lands have been hardened and wherein no treatment toremove metal has been applied to the land surfaces after said hardeningexcept, optionally, for the removal of scale produced by said hardening.13. A outer joint member according to claim 12 wherein the depth of eachrelief portion is no greater than 150 microns with respect to the landsurface at the ends of the relief portion.
 14. An outer joint memberaccording to claim 13 wherein the depth of each relief portion isbetween 50 and 100 microns with respect to the land surface at the endsof the relief portion.
 15. An outer joint member according to claim 13wherein the depth of each relief portion is between 30 and 50 micronswith respect to the land surface at the ends of the relief portion. 16.A method of making an outer joint member of a joint as claimed in claim1 in a finished state ready for use in said joint comprising making ablank (50) for the member, simultaneously or sequentially producing, thetracks (17), the lands (18) and the relief portions (25; 32, 33; 36: 42)in the surfaces of said lands of said outer joint member and then heattreating said member to harden the surfaces of the lands and tracks butapplying no further treatment to said land surfaces to remove metaltherefrom after hardening of the member except, optionally, for theremoval of scale produced by said hardening.
 17. A method of making anouter joint member according to claim 16 wherein the depth of eachrelief portion is no greater than 150 microns with respect to the landsurface at the ends of the relief portion.
 18. A method of making anouter joint member according to claim 17 wherein the depth of eachrelief portion is between 50 and 100 microns with respect to the landsurface at the ends of the relief portion.
 19. A method of making anouter joint member according to claim 17 wherein the depth of eachrelief portion is between 30 and 50 microns with respect to the landsurface at the ends of the relief portion.